Well, as we know that properly maintaining and cleaning the plastic lenses of sunglasses will make them look better and last longer. No matter fashionable or functional sunglasses, they should not be cleaned with napkins, toilet tissue or paper towels. The reason is that these objects can scratch the delicate plastic, remove the protective UV coating. So when there are some sweet strains on your sunglasses, you should clean them carefully in a right way. First, you should wash your hand so that it can not make your sunglasses be infected. Then you can warm your soft cloth which is used to rap the lenses which have sweet strain on. Remember you should use warm water when you do this. Finally, you can clean your sunglasses with resolution.